Bees are sometimes exceedingly pleasant to capture, for many of them emit the most agreeable scents; some a pungent and refreshing fragrance of lemons; others the rich odour of the sweetest-scented rose; and some a powerful perfume of balsamic fragrance and vigorous intensity. These have their set-off in others which yield a most offensive smell, to which that of garlic is pleasant, and assafœtida a nosegay. These odours must have some purpose in their economy, but what it may be has not been ascertained.
They present very frequently remarkable disparities of structure and appearance in the sexes, so much so that its infrequency is rather the exception than the rule, and nothing in many cases but practical experience can associate together the legitimate sexes. Differences of size are the simplest conditions of these distinctions, for they occur also in individuals of the same sex. Differences of colour, consisting in increased intensity in the males, are also usually easily recognized; but the relative length and structure of the antennæ is a more marked disparity, and the development is always in favour of the male. The differences in the compound eyes are conspicuous in our native genera only in the drone, where they converge on the vertex, and throw the stemmata down upon the face. I have before alluded to special peculiarities in the legs when treating of those limbs. In the wings there are occasional differences, but so slight as not to require, in a general survey, special notice; but wherever they occur it is always in the male that the greatest extension of those limbs is found. The differences in the termination of the abdomen I have noticed above, and these sexual peculiarities in some genera are very marked. The spines which arm it in _Anthidium_ and _Osmia_, and its peculiar structure in _Chelostoma_ we can account for; but we have not the same clue to their uses in _Cælioxys_, in which the action of the abdomen is upward, and not downward, as in the others.
The association of the legitimate partners of our native species has been to a great extent already accomplished and recorded; therefore, in this case, with the requisite guides to further instruction at hand, the commencing entomologist will find no obstruction, but may register the observations of his own experience to verify the discoveries of his predecessors.